Many ground engagement tools, drill bits, cold planers, pavement milling tools, asphalt picks, mining picks, hammers, and other wear-resistant tools experience abrasive conditions, which can cause accelerated wear of the components. This wear can cause operational problems such as underperformance of ground engagement tools and pavement degradation tools, increased demands on the machine components that operate the wear-resistant tools, and the expense and downtime resulting from having to frequently replace the worn components. Accordingly, some wear parts are fabricated with a wear surface having enhanced material properties.
Properties such as hardness are important factors that determine the wear resistance of a metal. Hardness relates to the resistance of the metal to scratching or abrasion. The higher the hardness of the metal, the greater its resistance to wear. In some cases, after fabrication of a metal component, a heat treatment operation may be performed to increase the hardness of the component surface. As a result of the heat treatment operation, a layer of material at the component surface may have a higher hardness than the bulk of the component. The increased hardness at a surface that will experience wear improves the wear resistance and prolongs the useful life of the component. Although in general, surface hardening improves wear resistance, for components that experience very high rates of wear, increased surface hardness produced by a heat treatment operation may be insufficient for a beneficial improvement in wear resistance. Such components may be hardfaced and then heat treated to further improve wear resistance.
Hardfacing is a low cost method of depositing wear resistant surfaces on metal components to extend service life. The American Welding Society defines hardfacing as “[a] surfacing variation in which surfacing material is deposited to reduce wear.” The term surfacing is defined as “[t]he application by welding . . . of a layer, or layers, of material to a surface to obtain desired properties or dimensions, as opposed to making a joint.” AWS A3.0 Standard Welding Terms and Definitions. As opposed to a hardening heat treatment operation, which involves changing the microstructure and mechanical properties of the component surface, hardfacing involves the deposition of a new material on the base material of the component. In general, the clad material may have a similar or a different composition than the base material. Hardfacing may be performed using a number of welding (or cladding) techniques. These known techniques can be broadly classified into three categories as arc welding (or arc cladding), thermal spraying, and laser-based cladding. The current disclosure is directed to hardfacing of a metal component using a laser cladding process.
A wide variety of hardfacing materials have been satisfactorily used on drill bits, pavement degradation tools, and other wear-resistant tools. A frequently used hardfacing material includes sintered tungsten carbide (WC) particles in an alloy steel matrix deposit. Other forms of tungsten carbide particles may include grains of monotungsten carbide, ditungsten carbide and/or macrocrystalline tungsten carbide. U.S. Pat. No. 7,469,972 to Hall et al. (“the '972 patent”) discloses a wear-resistant tool that comprises first and second cemented metal carbide segments chemically bonded together at an interface by brazing. One of the metal carbide segments may be bonded to a superhard material such as polycrystalline diamond. The cost of wear-resistant tools manufactured using the process disclosed in the '972 patent may be prohibitively expensive as a result of the use of large chunks of polycrystalline diamond, which are bonded to the contact surface of the tool. On the other hand, the less expensive methods of hardfacing using only tungsten carbide particles in an alloy steel matrix deposit may not provide the required level of protection against wear and erosion, and would therefore benefit from solutions that increase the wear resistance while controlling the costs of the materials and methods.
The method of the present disclosure is directed at solving one or more of the problems set forth above and/or other problems in the art.